1. Field of the Invention
The present invention relates to an electroluminescent device having a transparent electrode and a plurality of counter electrodes and capable of emitting light when an ac electric field is created between the transparent electrode and each counter electrode and, more particularly, to an electroluminescent device suitable for application to displaying characters, patterns or numerals as a display element.
2. Description of the Prior Art
The electroluminescent device (hereinafter abbreviated the "ELD") has been widely used as a display for various equipment. Such a display incorporating an ELD, in general, has a liquid crystal display element and uses the ELD as means for emitting background light. In recent years, there has been proposed a display or a level meter, which uses light emitted by an ELD directly for displaying patterns or indicating time.
When the ELD is used as a display element, the electroluminescent segments of the ELD must be activated selectively by applying an electric field through a wiring pattern across a transparent electrode and selected counter electrodes. Generally, an insulating overcoating layer is formed by printing over the counter electrodes and the wiring pattern is formed by printing on the insulating overcoating layer.
In forming the wiring pattern on the overcoating layer, the overcoating layer must be printed in regions other than those corresponding to the counter electrodes, and then the wiring pattern must be formed in the regions corresponding to the counter electrodes. Such a procedure requires complicated manufacturing processes and increases the cost of the ELD. Furthermore, since the overcoating layer cannot be formed in a thickness sufficient for the dielectric insulation of the counter electrodes from the wiring pattern, a weak electric field is applied to portions of the fluorescent layer corresponding to the wiring pattern to cause the portions of the fluorescent layer to become dimly luminous in the shape of the wiring pattern.